The ability to enter Japanese text into an English-language document or computer application is useful in certain applications and international correspondence. However, the complexity of the Japanese written language poses several challenges for efficient text entry in non-Japanese computers or other electronic devices.
The Japanese written language contains three separate character sets. Simple Japanese characters representing phonetic syllables are represented by the hiragana and katakana character sets. Hiragana characters, which are characterized by a cursive style, are typically used for words native to Japan. Katakana characters, which are characterized by a more angular style, are typically used for words borrowed from other cultures, or for emphasis and sound effects. The third character set in Japanese is kanji. Kanji are the complex Japanese characters borrowed from the Chinese language. There are over 9000 kanji characters in the Japanese language. Approximately 4000 kanji are used on a semi-regular basis, while knowledge of 2000 kanji is generally required to read a newspaper or get around in Japan. One additional representation of written Japanese is the roman character or "romaji" character set. Romaji are romanized representations of Japanese words based on the sound of a character, and are typically used only to facilitate electronic input of Japanese characters in a computer, or to aid foreign students in the study of Japanese.
Common methods of Japanese text entry for computers and like devices typically require the use of dedicated Japanese character keyboards or standard U.S. "QWERTY" keyboards which have been adapted for Japanese use. Both approaches, however, are quite cumbersome and inefficient. One disadvantage of the Japanese character keyboard is the high number of keys required to represent the basic Japanese character set. A typical Japanese keyboard may have upwards of 100 keys depending on how the various character variations are represented. A disadvantage of the adapted U.S. QWERTY keyboard approach is that often complex keystroke combinations must be mastered in order to generate the proper Japanese character, since an alphabetical arrangement of roman letters is not a natural order for entering Japanese text. A second disadvantage of this method is that the standard QWERTY keyboard contains many alphabetic keys which are not used in the Japanese character system. This is due to the fact that Japanese is not normally written with roman characters and can be represented in romaji through only a subset of the 26 roman letters.
Many electronic devices are making increased use of on-screen or "virtual" keyboards to facilitate text entry. This is especially true with devices such as Personal Digital Assistants (PDA's), or computer or communications devices which feature minimal keyboards or keypads for text entry. On-screen keyboards are also used in computer-based communications systems in which a standard computer monitor and keyboard are not utilized. Examples of such systems include the Network Computer (NC) and similar dedicated network server systems. An on-screen keyboard is a picture of a keyboard with each key represented as a separate selectable graphic object. A cursor control device, such as an arrow button or similar directional control, is used to move a cursor or similar on-screen indicator to select a particular character. In a typical text entry situation, the cursor is moved to a desired key with the direction controls, and that key is selected or `entered` using a separate button on the device. This process is then repeated for each letter in the word.
Existing systems which use on-screen keyboards to enter Japanese text are typically based on either a full roman QWERTY arrangement or a full Japanese character arrangement. However, because of display and text entry constraints of on-screen keyboards, the problems posed by regular keyboards with respect to Japanese text entry are increased in the case of on-screen keyboards. For example, the implementation of a standard Japanese on-screen keyboard would likely produce a crowded display of characters that would be difficult to distinguish in a low-resolution or limited screen area. Likewise, the use of a standard U.S. QWERTY on-screen keyboard for Japanese text entry would likely require a complex input routine involving many keystrokes to move among common romaji characters since a standard QWERTY layout is an inherently inefficient arrangement for romaji.
It is therefore desirable to provide a system which allows the entry of Japanese text into an electronic device with minimum required user input, thereby speeding entry of the text and reducing the display area occupied by the keyboard.